Coil mounting structure



Sept. 3, 1963 COIL G. M. STONE MOUNTING STRUCTURE Filed Oct. 10, 1961 FIG, 2

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l H I F] I FIG. 9 72 7 u n u u INVENTOR. I: E

u u n n GEORGE M. STONE ATTORNEY United States Patent 3,102,940 COIL MOUNTING STRUCTURE Ge'orge M. Stone, Naperville, Ill., assignor to General Electric Company, a corporation of New York Filed Oct. 10, 1961, Ser. No. 144,163 Claims. (Cl. 219 -19) The invention relates to heating coil mountings and more particularly to insulating means for mounting a plurality of open-helix, heating coils in spaced, parallel relationship. v

The usual technique for assembling open-helix, heating coils is to thread a coil through a series of spaced, (closed bore insulators, either before or after the insulators are afiixed to the ultimate mounting surface. The assembly process is quite diiiicult in that a resilient coil must be threaded delicately through insulators spaced a (distance apart. Since the coil must be threaded through the bores, the open bores can have no impediments to axial movement of the coil. Usually, open coil heating units are used for air heating, and because it is diificult to obtain uniform heat transfer over the length of a coil, certain portions will inevitably be at a higher temperature than others. It has been found that under such conditions, portions of a coil will tend to sag and slide axially so that the original length of coil bet-ween adfiacent insulators is disrupted and certain areas of the coil are elongated. Such elongation can lead to grounding and shorting of the coil against adjacent metallic objects;

It is therefore an object of the invention to provide an improved structure for insulatedly mounting open helix heating elements whereby the resultant assembly is readily amenable to mass production methods and capable of extended, trouble-free life. i

It is a further object of the invention to provide a coilmounting insulator comprising identical sections which may be clamped about one or more heatercoils, and provide means for holding the coils against axial movement While insuring cooling air flow to the coils within the area encompassed by the insulator. 1

To achieve these and other objects, the present invention utilizes insulators each of which comprises a yokelike spacer member, the ends of which each define a substantially semicircular channel of narrow length axially. The channels are constructed so that their axes are perpendicular to the length of the spacer member. Into each of the open channels of one of these insulators may be laid an open helix resistance heater coil, whereupon the coils each extend in mutually parallel relationship. Asecond, identical, spacer member is then placed with the channels covering the coil sections within thechannels below, thereby forming a multiple bore insulating mounting support for the coils. By means such as a U- shaped tensile metal clip fitted about the two spacer members, the assembly of insulators and coils is easily handled for attachment to a mounting surface.

An important feature of, the insulators resides in the provision of a V-shaped ridge centrally within each channel portion, and extending transversely of the axis of the channel. When the spacer members are assembled as aforesaid, the upper and lower ridges enter within a single coil convolution. This increases the pitch angle of the helix within the insulator and prevents there being more than one turn of wire in a location in which ventilation is restricted, even though the ends of 'the'adjacently assembled channel portions are shaped to provide an air 'gap which allows cooling air currents to circulate through the coil mounting bore. Additionally, of course, the ridges cooperatively grip the wire to prevent the axial shifting thereof.

The invention both as to-its organization and principle 7 2 of operation, together With further objects and advantages thereof, will best be understood by reference to the following specifications taken in connection with the accompanying drawings in which:

FIG. 1 is a front elevational view of a heat panel uti-- lizing a plurality of mounting structures incorporating the invention herein;

FIG.2 is a side elevational view of the panel of FIG. 1; FIG. 3 is a front elevational view of a single mounting as used in FIG. 1;

FIG. 4 is a side elevational view of the mounting structure of FIG. 3;

FIG. 5 is a top plan View of the structure of FIG. 3; FIG. '6 is a side elevational view of a single insulating spacer member of the FIG. 3 structure;

FIG. 7 is a bottom view of the insulator of FIG. 6; FIG. '8 is a side elevation of a mounting structure accommodating three heating coils; and

FIG. 9' is a fragmentary plan view of the fixture on which the heating coils are first assembled to the spacer members.

Now turningto FIGSfl and 2, there can be seen a circular metal plate 10 which comprises the heating element base and heat reflector of an appliance such as a domestic clothes dryer. The plate has an inturned annular flange 12; radially inwardly thereof are a plurality of annular bafliled openings 14 arranged to provide a substantially annular air passage through the plate. inwardly adjacent the baffied openings are a pair of side-by-side mounted helical resistance coils which are combined to act as substantially annular double-ring heater. These lcoils, numbered 20 and 2-2 are insulated mutually and from the plate, and are individually connected at their free ends to suitable terminals 24, 2 6, 28 and 30 for connection to a source of energizing current.

.' Maintaining the spacing of the helix coils 20' and 22 are a series of mounting structures 40 embodying the present invention. Each mounting structure 40 as shown in detail'in FIGS. 3, 4 and 5 includes a pair of identical spacing members or supports 42 clamped together in a face-to-face relationship by means of a metal mounting clip 44. Said spacing members are advantageously formed of heat-resistant, electrically insulating ceramic.

Mounting clip 44 is a substantially U-shapecl tensile memher which sits astraddle the two identical insulators 4-2 and is designed to key into suitable slit openings 4'5 in the base plate iii. The parallel legs 46' of the U-member 44, of course, fit through the cooperatingly spaced slits 45 in the plate to anchor and space the insulators and coils from the panel.

Turning now to FIGS. 6 and 7, a spacer member or support 42. primarily comprises a yoke-like structure of limited Widthdimension, having a central spacer bar or member 519 at each extremity of which there is a coil-holding section 52. Each such section "52 includes a substantially semicircular open channel 54 with the axial center line of the channel substantially in the same plane as the surface 55 of the spacer 50. The radius of each channel is substantially equal to the maximum radius of the helical coils 2d and 2-2. At the center (in an axial direction) of each channel there is a narrow rib 56, 'V-shaped in cross section, which intrudes segmentally into the channel for a short distance. At the outer extremity of each channel *a terminating wall extends horizontally for the greater portion of its width dimension, and then curves into a narrow finger 62 which extends slightly past the bottom wall surface 55 of the spacer bar 56. As appears in FIG. 4, the respective walls on of the upper and lower elements 42 are spaced one above the other and the fingers -62 of adjoined insulators are in an axially spaced interdigited relation. This promember.

parts to achieve the proper lit.

ary purpose of insulating the coils from accidental con-.

tact with the metallic mounting member. This insulating feature is especially importantat the coil ends where the coil conductor must extend obliquely toward a terminal such as 24, past the edge of the mounting clip If these shoulders were to be omitted, and as the coil ends loosen due to intermittent heating and cooling, these coil ends would invariably strike one or more of the mounting members. This contact would, of course, ground or short the coil involved.

Each insulator spacer element further includes, in the central section, a pair of vertically extending pins aligned diagonally on either side of the center line of the spacing bar 50. Diagonally oblique to and aligned with these pins [are a'pair of circular recesses 68 which aredesigned to accept pins such as 66 of the complementary spacer member 42. Thus, when two identical members 42 are to be joined in a mounting structure 40', theportions 55 i of the spacer bars of the insulators are juxtaposed and the pins are fitted into the matching holes. By providing these recesses diagonally aligned as are the :dowel pins, there is no problem of mismatch and juggling of identical members there is provided a pair of parallel substantially circular bores to insulatedly space apart coils 20 and 22. In the embodiment of FIG. 8, the respective members 42:: accommodate three coils; said members have similar V-shape-d ridges 56a, and are otherwise substantially identical to the previously described structures. Clips -44 are used to secure and mount the assemblies.

The apparatus found most advantageous for assemhim}; the coils is schematically. shown in FIG. 9. A flat fixture 70 is provided with upstanding pairs of walls 71, 72 which are spaced apart sufliciently to snugly receive the spacer members 42. The walls of each pair engage only the portions 52 of the upper and lower members 42, thus leaving the portion '50 thereof exposed. An opening 73 at each pair of walls accommodates the passage of the mounting clip 44, as ater described. The pairs of walls 71, 72'are spaced along the fixture 70 so that when each of the pairs is occupied by a lower member 42, the workman'can take a tight-Wound heating coil of fixed length, stretch the coil uniformly and set it into the horizontally aligned, upwardly facing channel portions of the succession of members 42. The workman then places an upper member 42 within the pairs of With this joinder of 4 v axial movement of the coils. Further, these centrally positioned ridges allow air currents, generated by the heat differentials induced during heating, to penetrate each channel and thus minimize any localized overheating of the coil. It will be noted from FIG. 4 that the width of the coil-holding sections 52 and the relation of base thickness to height of the ridges 56, are such that when the respective elements are assembled about a heater coil stretched the normal amount, the entry of the ridges Walls, with the alignment pins and holes establishing the proper relationship or the upper and lower members. A

mounting member 44 is compressed about the assembled spacer sections, with the legs 46 of the members being accommodated Within the openings 73. The'entire subassembly may be removed from the fixture 70*; the mounting clips '44 embrace the assembled pair of elements 42 and secure them against separation. During the assembly, the ridges 56 have entered between adjacent turns of the heating coil, thus securing the coil against longi tudinal displacement relative to the members 42. The workman may then serially insert the legs of the mounting clips through the apertures 45 in the mounting plate 10. f The shoulders 75 and the outwardly sprung tabs 76 engage on opposite faces of the plate 10 and properly position the assembly. It should be noted that the spacing between the openings 45 will be as desired to stretch out the coils to place them under sufiicient tension so that as the coils heat andtend to sag, they cannot sag enough to contact the plate Ill. The ridges 56 prevent a through each bore axially,

between adjacent turns of the coil increases the pitch angle so that substantially only the wire of. a single turn is wholly within the insulator. Hence, good ventilation into each bore is ensured and as a result hot spots due to an encirclment of the resistance wire by the insulators, are minimized.

The previously described hook-end construction whereby the hook ends terminate in narrow fingers extending past the centerline of the coil bore along only a small. portion of the bore width tends to provide an open air space, as can be seen best in FIG. 4, through which air how can radially enter the, coil-holding area to further cool the coil-holding bore and minimize localized hot spots and failures resulting from such a condition. Further, this finger-end construction insures that no single conductor can escape outwardly of a coil-holding bores The staggering of cooperating fingers 62 (see FIG. 4)' is such that any conductor sagging outwardly will be held within the bore by one or the other of the fingers 62.

With the coils secured to the metal panel, and spaced from the panel by the mounting clip legs 46, air currents will llcw through the bafi'led openings 14 past the heatersto the area being heated. The circulating air will tend to draw away heat generated by the heaters both in the area between heaters and to a lesser degree Within the insulating bores holding the coils.

From the above description, it will be apparent that the invention provides for making a heating coil assembly in which there are a minimum of opportunities for mistakes by even the most unskilled workman, and in which the ultimate heating unit is protected against failure in operation. 7

While there has been described what 'israt present thought to be the preferred embodiment of the invention, it willbe understood that various modifications may be made therein and it is intended to cover in the ap pended claims all such modifications asr'all within the true spirit and scope of the invention.

What is claimed is:

1. In a heating unit assembly Whichcornprises a base plate, and a plurality of open helix resistance coils spaced from said plate and spaced from one another to form a plurality of heating annuli about said plate; means for mounting said coils to said plate and insulating said coils from said plate-comprising a plurality of split insulator sulatorspositioned complementarily together to form two parallel, spaced open bores, a narrow V-shaped ridge extending vertically inward from each of said insulators I at the center thereof into each said bore from above and below, said ridges positioned to extend segmentally into a helix and hold said helix against movement axial to said bore, a substantial air gap between the upper and lower segmental ridges to allow air currents to pass the outermost end of each of said insulators being formed with a finger at a side wall thereof, said fingers in the assembled insulators being in axially spaced, interdigited relation to provide an air opening to said bore at the outermost tip of said mounting, said fingers respectively extending beyond the central plane of the bore whereby no portion of said helix conrductor can escape said bore through said air opening.

2. A mounting structure for an open helix heater coil, comprising a pair of identical insulating members, each including a central spacing bar having at each end a. substantially semicircular coil-supporting portion, each i '5 said portion having a V-shaped ridge extending chordally there/across, the radius of each said 'coil-supporting portion being substantially that of the heater coil and the relationship of the Width of Said portions and the base thickness and height of said V-shaped ridge being such that upon clamping'said insulating membersv in face-tof-ace relation about the coil the entry of the respective ridges into the coil distorts the coil so that substantially only a single turn thereof is enclosed by said coil supporting portions, and means comprising a resilient clip embracing the insulating members about the spacing b ar portions thereof to hold said members in operating relationship to said coil. p

t 3. The mounting structure according-to claim 2 in which the distal ends of each said insulating member have atone side Wall only, a finger portion which .afiords additional 'encirclement of saidheater coil, the transverse Width of said finger portions being such that when said members are clamped about the coil the fingers are inter-digitatedin transverse-spaced relation to provide a radially disposed passage communicating with the interior of said coil. I V a 4. The mounting structure according to claim 2 in which the respective spacer bar portions are defined by shoulders engageable with the respective side edges of said resilient clip to prevent angular displacement of said members relative to said clip.

5. In a heating unit assembly comprising a base plate and a plurality of open helix heater coils arranged in spaced parallel relation thereon, the improvement in means for supporting said coils'inspaced relation to said plate, comprising, in combination: first and second elongated, identical, yoke-like members of rigid insulation material, each said member having a'rectangular central portion and arcuate portions extending laterally thererespective ends of each channel, said finger means, further, substantially completing the periphery of the respective cylindrical passages, at least one insulating Wedge means extending chordally across each said passage, said Wedge means having a maximum radial depth effiecti-ng penetration thereof into the interior of said helical coil, and .a resilient clip member embracing said body portion in engagement with all four sides thereof, said clip memher having elongated resilient leg portions adapted to penetrate an opening in said plate in resilient engagement with the margins thereof.

References Cited in the file of this patent UNITED STATES PATENTS 

2. A MOUNTING STRUCTURE FOR AN OPEN HELIX HEATER COIL, COMPRISING A PAIR OF IDENTICAL INSULATING MEMBERS, EACH INCLUDING A CENTRAL SPACING BAR HAVING AT EACH END A SUBSTANTIALLY SEMICIRCULAR COIL-SUPPORTING PORTION, EACH SAID PORTION HAVING A V-SHAPED RIDGE EXTENDING CHORDALLY THEREACROSS, THE RADIUS OF EACH SAID COIL-SUPPORTING PORTION BEING SUBSTANTIALLY THAT OF THE HEATER COIL AND THE RELATIONSHIP OF THE WIDTH OF SAID PORTIONS AND THE BASE THICKNESS AND HEIGHT OF SAID V-SHAPED RIDGE BEING SUCH 